Semiconductor package with air pressure sensor

ABSTRACT

A semiconductor package having an air pressure sensor and methods to form a semiconductor package having an air pressure sensor are described. For example, a semiconductor package includes a plurality of build-up layers. A cavity is disposed in one or more of the build-up layers. An air pressure sensor is disposed in the plurality of build-up layers and includes the cavity and an electrode disposed above the cavity. Also described are various approaches to fabricating a semiconductor package having a hermetically sealed region.

TECHNICAL FIELD

Embodiments of the invention are in the field of semiconductor packagesand, in particular, semiconductor packages with air pressure sensors.

BACKGROUND

Today's consumer electronics market frequently demands complex functionsrequiring very intricate circuitry. Scaling to smaller and smallerfundamental building blocks, e.g. transistors, has enabled theincorporation of even more intricate circuitry on a single die with eachprogressive generation. Semiconductor packages are used for protectingan integrated circuit (IC) chip or die, and also to provide the die withan electrical interface to external circuitry. With the increasingdemand for smaller electronic devices, semiconductor packages aredesigned to be even more compact and must support larger circuitdensity. For example, some semiconductor packages now use a corelesssubstrate, which does not include the thick resin core layer commonlyfound in conventional substrates. Furthermore, the demand for higherperformance devices results in a need for an improved semiconductorpackage that enables a thin packaging profile and low overall warpagecompatible with subsequent assembly processing.

Furthermore, for the past several years, microelectromechanical systems(MEMS) structures have been playing an increasingly important role inconsumer products. For example, MEMS devices, such as sensors andactuators, can be found in products ranging from inertial sensors forair-bag triggers in vehicles to micro-mirrors for displays in the visualarts industry and, more recently, in mobile applications such as airpressure sensors for altitude sensing. As these technologies mature, thedemands on precision and functionality of the MEMS structures haveescalated. For example, optimal performance may depend on the ability tofine-tune the characteristics of various components of these MEMSstructures. Furthermore, consistency requirements for the performance ofMEMS devices (both intra-device and device-to-device) often dictatesthat the processes used to fabricate such MEMS devices need to beextremely sophisticated.

Although packaging scaling is typically viewed as a reduction in size,the addition of functionality in a given space is also considered.However, structural issues may arise when attempting to packagesemiconductor die with additional functionality also housed in thepackage. For example, the addition of packaged MEMS devices may addfunctionality, but ever decreasing space availability in a semiconductorpackage may provide obstacles to adding such functionality.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1A-1E illustrate cross-sectional views of various operations in amethod of fabricating a reference cavity using a continuous via ring, inaccordance with an embodiment of the present invention.

FIGS. 2A-2E illustrate cross-sectional views of various operations in afirst method of fabricating structural support for a reference cavity,in accordance with an embodiment of the present invention.

FIGS. 3A-3F illustrate cross-sectional views of various operations in asecond method of fabricating structural support for a reference cavity,in accordance with an embodiment of the present invention.

FIGS. 4A-4C illustrate cross-sectional views of various operationalstates of a pressure sensor having an underlying reference cavity, inaccordance with an embodiment of the present invention.

FIG. 5A illustrates a cross-sectional view and corresponding top view ofan air pressure sensor having a single large opening to ambientconditions, in accordance with an embodiment of the present invention.

FIG. 5B illustrates a cross-sectional view and corresponding top view ofan air pressure sensor having several small openings to ambientconditions, in accordance with an embodiment of the present invention.

FIGS. 6A and 6B illustrate schematics and equations for determininganalytical calculations for sensing air pressure in a capacitive manner,in accordance with an embodiment of the present invention.

FIG. 7A is a plot of capacitance change versus negative pressuredifference, in accordance with an embodiment of the present invention.

FIG. 7B is a plot of capacitance change versus positive pressuredifference, in accordance with an embodiment of the present invention.

FIG. 8 illustrates a plan view and corresponding cross-sectional view ofa magnetically-actuated resonant beam air pressure sensor, in accordancewith an embodiment of the present invention.

FIG. 9 illustrates schematics and equations for determining analyticalcalculations for sensing air pressure for a magnetically-actuatedresonant beam air pressure sensor, in accordance with an embodiment ofthe present invention.

FIG. 10A is a plot of estimated response frequency for a magneticallyactuated air pressure sensor, in accordance with an embodiment of thepresent invention.

FIG. 10B is a plot of estimated response sensitivity, for a magneticallyactuated air pressure sensor, in accordance with an embodiment of thepresent invention.

FIGS. 11A-11P illustrate cross-sectional views of various operations ina process flow using copper mesh support for lamination of ABF above areference cavity, in accordance with an embodiment of the presentinvention.

FIGS. 12A-12Q illustrate cross-sectional views of various operations ina process flow using a thin plate to support lamination of ABF above areference cavity, in accordance with an embodiment of the presentinvention.

FIGS. 13A-13T illustrate cross-sectional views of various operations ina process flow for fabricating a magnetically actuated pressure sensor,in accordance with an embodiment of the present invention.

FIG. 14 is a schematic of a computer system, in accordance with anembodiment of the present invention.

DESCRIPTION OF THE EMBODIMENTS

Semiconductor packages with air pressure sensors are described. In thefollowing description, numerous specific details are set forth, such aspackaging architectures, in order to provide a thorough understanding ofembodiments of the present invention. It will be apparent to one skilledin the art that embodiments of the present invention may be practicedwithout these specific details. In other instances, well-known features,such as integrated circuit design layouts, are not described in detailin order to not unnecessarily obscure embodiments of the presentinvention. Furthermore, it is to be understood that the variousembodiments shown in the Figures are illustrative representations andare not necessarily drawn to scale.

One or more embodiments described herein are directed to semiconductorpackages having one or more microelectromechanical systems (MEMS)structures incorporated therein. In one such embodiment, an air pressuresensor is fabricated in package build-up layers. One or more embodimentspertain to one or more air pressure sensors, bumpless build-up layer(BBUL) packaging, electrostatic sensors, hermetic sealing, magneticallyactuated sensors, or MEMS technologies. Structures or devices describedherein may have applications in one or more of mobile/consumer productswhich use BBUL technology.

BBUL embedded packaging technology may be considered for mobile chippackaging technology. Air pressure sensors are important for consumermobile devices, providing accurate altitude and barometric measurements.Accordingly, in an embodiment, an air pressure sensor is fabricated inor via BBUL technology. As a comparison, conventional air pressuresensors are typically relatively thick compared to a silicon die.Embedding of such sensors into a package for a silicon die may increasepackage thickness and cost, rendering the overall package lessattractive. Furthermore, MEMS-based air pressure sensors typically use ahermetically-sealed pressure chamber to provide a reference airpressure. Accordingly, in an embodiment, air pressure sensors arefabricated directly in BBUL build-up-layers. Compared with embeddingsilicon based pressure sensors, approach described herein retain asuper-thin feature of BBUL, and also mitigate costs associated withseparately fabricated air pressure sensors.

Thus, embodiments described herein target building or fabricating airpressure sensors or other MEMS devices using packaging build-up-layers.It is to be understood that a challenge of using such build-up layertechnology for air pressure sensors may be a need for the manufacture ofa hermetically-sealed package. Due to the porous nature of standardAjinomoto build-up film (ABF) build-up layers (or other similarlaminated materials), laminated ABF layers may not be adequate forforming an air pressure cavity. In order to address such issues, in anembodiment, a copper via ring is used to form a hermetically sealedpackage for the reference air pressure. The top surface of the sealedpackage acts as a diaphragm and is the bottom electrode for theelectrostatic sensing mechanism. In this arrangement, as the airpressure of the environment changes, sensed capacitance between the twoelectrodes changes. Sufficient sensitivity may be achieved for theranges of interest for consumer products. In one embodiment, a“continuous via ring” method is adaptable for other MEMS applicationsrequiring a reference air cavity or hermetic sealing of structures.

Accordingly, a continuous via ring may be fabricated for MEMS-basedpackaging. For example, FIGS. 1A-1E illustrate cross-sectional views ofvarious operations in a method of fabricating a reference cavity using acontinuous via ring, in accordance with an embodiment of the presentinvention. Such an approach may be used where it is difficult to form asealed cavity for a pressure sensor by using only ABF, due to theporosity of the ABF material.

Referring to FIG. 1A, a stack 100 is provided including a firstinsulating laminate layer 102, a plating layer 104 (e.g. a copperplating layer), and a second insulating laminate layer 106. Vias 108(e.g., copper vias) are formed through the second insulating laminatelayer 106, in contact with the plating layer 104, forming a foundationfor a “continuous via ring,” as depicted in FIG. 1B. Referring to FIG.1C, a cavity 110 is formed in second insulating laminate layer 106,between vias 108 and exposing plating layer 104, e.g., by an oxygenplasma etch process. A third insulating laminate layer 112 is thenformed over the structure of FIG. 1C, as depicted in FIG. 1D. Referringto FIG. 1E, a continuous via ring is generated by forming second vias114 in the third insulating laminate layer 112, and forming a topmembrane plating layer 116, e.g., a copper membrane plating layer, abovethe third insulating laminate layer 112. In an embodiment, the coppercontinuous via ring (from vias 108 and 112), as well as the top copperplating 116 and bottom copper plating 104 form a hermetic seal over theair pressure cavity 110. It is to be understood that where copper isdiscussed throughout, other similar metals may be used insteadInsulating lamination layers described herein may, in an embodiment,refer to alternating conducting and dielectric layers, the latter being,e.g., an ABF or ABF-like layer.

Structural support for ABF lamination may be needed since the large areaof the cavity 110 may cause lamination problems and collapse during thelamination process. Thus, efforts may be made to prevent or inhibitcavity collapse in a build-up layer process. As a first example, FIGS.2A-2E illustrate cross-sectional views of various operations in a firstmethod of fabricating structural support for a reference cavity, inaccordance with an embodiment of the present invention.

Referring to FIG. 2A, a stack 200 is provided including a firstinsulating laminate layer 202, a plating layer 204 (e.g. a copperplating layer), and a second insulating laminate layer 206. Vias 208(e.g., copper vias) are formed through the second insulating laminatelayer 206, in contact with the plating layer 204. Additionally, a meshpattern 209 is formed, as depicted in FIG. 2B. Referring to FIG. 2C, acavity 210 is formed below the mesh pattern 209, e.g., by an oxygenplasma etch process. A third insulating laminate layer 212 is thenformed over the structure of FIG. 2C, as depicted in FIG. 2D. Referringto FIG. 2E, a continuous via ring is generated by forming second vias214 in the third insulating laminate layer 212, and forming a topmembrane plating layer 216, e.g., a copper membrane plating layer, abovethe third insulating laminate layer 212. In an embodiment, the coppercontinuous via ring (from vias 208 and 212), as well as the top copperplating 216 and bottom copper plating 204 form a hermetic seal over theair pressure cavity 210. In an embodiment, the cavity 210 isstructurally supported by the overlying mesh pattern 209.

As a second example, FIGS. 3A-3F illustrate cross-sectional views ofvarious operations in a second method of fabricating structural supportfor a reference cavity, in accordance with an embodiment of the presentinvention.

Referring to FIG. 3A, a stack 300 is provided including a firstinsulating laminate layer 302, a plating layer 304 (e.g. a copperplating layer), and a second insulating laminate layer 306. Vias 308(e.g., copper vias) are formed through the second insulating laminatelayer 306, in contact with the plating layer 304, as depicted in FIG.3B. Referring to FIG. 3C, a cavity 310 is formed, e.g., by an oxygenplasma etch process. A thin plate 311, e.g., a thin polymeric or metalplate, is then formed or placed over the cavity 310, as depicted in FIG.3D. Referring to FIG. 3E, a third insulating laminate layer 312 is thenformed over the structure of FIG. 3D. A continuous via ring is generatedby forming second vias 314 in the third insulating laminate layer 312,and forming a top membrane plating layer 316, e.g., a copper membraneplating layer, above the third insulating laminate layer 312. In anembodiment, the copper continuous via ring (from vias 308 and 312), aswell as the top copper plating 316 and bottom copper plating 304 form ahermetic seal over the air pressure cavity 310. In an embodiment, thecavity 310 is structurally supported by the overlying thin plate 311. Inone such embodiment, the thin plate 311 has a higher glass transitiontemperature (Tg) than the ABF cure temperature such that the plate canprovide a mechanical shield during ABF lamination. In one embodiment,the thin plate 311 has some adhesion or stiction to copper in order toenable fixing the plate in position during ABF lamination. The seal,however, need not be perfect since the fabricated copper membrane may berelied on for hermeticity.

A capacitive pressure sensor may be fabricated to include a referencecavity as described above. For example, FIGS. 4A-4C illustratecross-sectional views of various operational states of a pressure sensorhaving an underlying reference cavity, in accordance with an embodimentof the present invention.

Referring to FIG. 4A, an air pressure sensor 400 is formed fromsuspended features 402 (e.g., suspended copper features) and electrodes404 (e.g., copper electrodes) formed above a reference cavity 410. As anexample, reference cavity 410 is formed based on the structure of FIG.1E (as depicted in FIG. 4A) but could be formed based on structures suchas those depicted in 2E or 3F as well. The air pressure sensor 400 isable to compare an ambient air pressure 420 with a reference airpressure 422 through capactive coupling (C), as depicted by the arrowsin FIGS. 4A-4C.

Referring again to FIG. 4A, the capactive coupling (C) is based on thedistance between the suspended member 402 and the underlying structureformed above reference cavity 410. In the case of FIG. 4A, the ambientair pressure 420 is the same as the reference air pressure 422, and thesystem is effectively at rest with a distance 430 between the suspendedmember 402 and the underlying structure formed above reference cavity410 essentially the fabrication height of the two layers. Referring toFIG. 4B, the ambient air pressure 420 is greater than the reference airpressure 422, and the distance 430 between the suspended member 402 andthe underlying structure formed above reference cavity 410 is greaterthan the fabrication height of the two layers. Referring to FIG. 4C, theambient air pressure 420 is less than the reference air pressure 422,and the distance 434 between the suspended member 402 and the underlyingstructure formed above reference cavity 410 is less than the fabricationheight of the two layers. Thus, in an embodiment, a barometric pressuresensor may be fabricated using a reference air cavity. The differencebetween ambient air pressure and reference air pressure is detected byan upwards or downwards deflection of the “diaphragm” formed to includethe reference cavity. The sensed capacitance reflects the extent ofdownward or upward deflection of the diaphragm.

Different configurations may be possible for forming an opening to anair pressure sensor. In a first example, FIG. 5A illustrates across-sectional view and corresponding top view of an air pressuresensor having a single large opening to ambient conditions, inaccordance with an embodiment of the present invention. Referring toFIG. 5A, an air pressure sensor 500A is formed to include a stiff toplayer/electrode 502A, a flexible bottom layer/electrode 504A, and areference air gap 506A. As an example, air pressure sensor 500A isfabricated based on the structure of FIG. 1E, e.g., as structure 400 ofFIG. 4A (as depicted in FIG. 5A) but could be formed based on structuressuch as those depicted in FIG. 2E or 3F as well. A single opening 550Ais included for exposure of the flexible bottom layer/electrode 504A, asdepicted in both views of FIG. 5A.

In a second example, FIG. 5B illustrates a cross-sectional view andcorresponding top view of an air pressure sensor having several smallopenings to ambient conditions, in accordance with an embodiment of thepresent invention. Referring to FIG. 5B, an air pressure sensor 500B isformed to include a stiff top layer/electrode 502B, a flexible bottomlayer/electrode 504B, and a reference air gap 506B. As an example, airpressure sensor 500B is fabricated based on the structure of FIG. 1E,e.g., as structure 400 of FIG. 4A (as depicted in FIG. 5B) but could beformed based on structures such as those depicted in FIG. 2E or 3F aswell. A plurality of openings 550B is included for exposure of theflexible bottom layer/electrode 504B, as depicted in both views of FIG.5B.

As described in association with FIGS. 4A-4C, a sensed capacitance maybe based on diaphragm motion in an air pressure sensor. FIGS. 6A and 6Billustrate schematics and equations for determining analyticalcalculations for sensing air pressure in a capacitive manner, inaccordance with an embodiment of the present invention. In particular,an analytical approach may be developed to model the sensitivity andrange of the air pressure sensor. Referring to FIG. 6A, for suchestimations, it is assumed that an air pressure sensor 600 includes atop electrode 602 that is rigid and a bottom electrode 604 that isflexible. A capacitance (C) is sensed between 602 and 604. The maximumdiaphragm deformation is estimated, and the deformation shape of thediaphragm is approximated to be pyramidal. The total capacitance is theintegral sum of each individual capacitance dC. Referring to FIG. 6B,square diaphragm deflection is determined by 606. Diaphragm deflectionis approximated by a pyramidal surface. The capacitance dC is integratedalong the length and width of the capacitor, via 608. The totalcapacitance 614 is then determined using 610 and 612.

An estimated response for a capacitive air pressure sensor may thus beprovided. As an example, FIG. 7A is a plot 700 of capacitance changeversus negative pressure difference, while FIG. 7B is a plot 702 ofcapacitance change versus positive pressure difference, in accordancewith an embodiment of the present invention. The estimated responsecurves for various sensor sizes using standard BBUL process conditionsinclude tgap=10 um, t=15 um, b=1 mm, 1.2 mm, 1.4 mm, 1.5 mm. For mobilebarometric pressure sensor applications, in an embodiment, the targetrange is approximately 0.5 atm to 1 atm (approximately 50 kPa to 100kPa), with a minimum detectable sensitivity of 50 Pa to 100 Pa. In anembodiment, referring to FIGS. 7A and 7B, sufficient sensitivity andrange is achieved with a 1.5 mm×1.5 mm diaphragm.

A magnetically-actuated beam may be used in conjunction with an airpressure sensor described above. For example, FIG. 8 illustrates a planview and corresponding cross-sectional view of a magnetically-actuatedresonant beam air pressure sensor, in accordance with an embodiment ofthe present invention. Referring to FIG. 8, a magnetically-actuatedresonant beam air pressure sensor 800 includes a diaphragm 802, resonantbeams 804 and an embedded magnet 806. Resonant beams are actuatedthrough interaction of an AC current with the permanent magnet. In theconfiguration depicted in FIG. 8, diaphragm deflection due to adifference in air pressure transduces a Z-displacement, which appliestension onto the resonant beam and increases the resonant frequency. Ingeneral, it is to be understood that structures may be more sensitive tochanges in resonant frequency, and so may have a higher sensitivity insuch a configuration.

FIG. 9 illustrates schematics and equations for determining analyticalcalculations for sensing air pressure for a magnetically-actuatedresonant beam air pressure sensor, in accordance with an embodiment ofthe present invention. Referring to FIG. 9, as was the case for FIGS. 6Aand 6B, the maximum diaphragm deflection is given by 902. Diaphragmdeflection induces Z-change, which applies tension to the resonantbeams, as depicted in 904. An analytical approach is used to model thesensitivity and range of the magnetically-actuated air pressure sensor.It is assumed that the change in diaphragm height contributes to achange in beam length which translates into beam tension and anincreased beam resonant frequency. In the analysis of FIG. 9, usingequations 906, 908, 910, 912 and 914, the beam is assumed to beresonating in the y-direction, though in principle, any resonant modemay be used.

A response may be estimated for a magnetically actuated air pressuresensor. For example, FIG. 10A is a plot 1000 of estimated responsefrequency (Hz), while FIG. 10B is a plot 1002 of estimated responsesensitivity (AHz/Pa), for a magnetically actuated air pressure sensor,in accordance with an embodiment of the present invention. Referring toFIGS. 10A and 10B, estimated response curves are for various sensorsizes using standard BBUL process conditions, e.g., tgap=10 um, t=15 um,b=1 mm, 1.2 mm, 1.4 mm, 1.5 mm. For mobile barometric pressure sensorapplications, in an embodiment, the target range is approximately 0.5atm to 1 atm (approximately 50 kPa to 100 kPa), with a minimumdetectable sensitivity of 50 Pa to 100 Pa. Beam length is 1000 um, andbeam resonant frequency is approximately 15000 Hz. With a 1.5 mm×1.5 mmdiaphragm, in an embodiment, a change in 50 Pa translates into afrequency change of more than 1 Hz, which is sufficient sensitivity forcertain applications.

A packaged MEMS device, such as an air pressure sensor, may be housed ina variety of packaging options. In a first example, FIGS. 11A-11Pillustrate cross-sectional views of various operations in a process flowusing copper mesh support for lamination of ABF above a referencecavity, in accordance with an embodiment of the present invention.

Referring to FIG. 11A, a die 1102 (which may include an amplifier, etc.)is placed on a thin substrate 1104 (e.g., silicon, etc.) adjacent anelectrode 1106 (e.g., a copper electrode), above a metal holder 1100(e.g., a copper holder). A laminate organic dielectric film 1108 isdisposed above the structure of FIG. 11A, as depicted in FIG. 11B.Referring to FIG. 11C, via hole drilling and electroplating is performedto provide vias 1110 and copper layer 1112 (again, a suitable metalother than copper may be used wherever copper is referred to herein). Aphotoresist layer 1114 is then formed and patterned to protect sensitiveareas, as depicted in FIG. 11D. Referring to FIG. 11E, oxygen plasmarelease is then performed to remove a portion of organic dielectric film1108 and to release structure 1116. Resist stripping is then performedto re-expose layer 1112, as depicted in FIG. 11F. Referring to FIG. 11G,lamination of an organic dielectric film 1118 is then performed. Viadrilling and electroplating is then performed to provide vias 1120 andcopper layer 1122, as depicted in FIG. 11H. Referring to FIG. 11I,organic dielectric film 1124 is then laminated on the structure of FIG.11H. Via drilling and electroplating is again performed to provide vias1126 and copper layer 1128, as depicted in FIG. 11J. Additionally, acopper mesh structure 1130 is electroplated for lamination support.Referring to FIG. 11K, photoresist layer 1132 is formed and patterned toprotect sensitive areas. An oxygen plasma release is the performed torelease structure 1134, as depicted in FIG. 11L. Referring to FIG. 11M,photoresist layer 1132 is then stripped, re-exposing layer 1128.Lamination of another insulator layer 1136 is then performed above thestructure of FIG. 11M, as depicted in FIG. 11N. Referring to FIG. 11O,via drilling and electroplating is performed to provide vias 1138 andcopper layer 1140. The copper holder 1100 is then removed, as depictedin FIG. 11P. A reference cavity 1150 and capacitor 1152 is thus formed.

Referring again to FIG. 11P, the structure as depicted can be viewed asa completed package for the semiconductor die included therein. However,for specific implementations, an array of external contacts (e.g., BGAcontacts) may optionally be formed above or below the structure depictedin FIG. 11P. The resulting structure may then be coupled to a printedcircuit board (PCB) or like receiving surface.

In a second example, FIGS. 12A-12Q illustrate cross-sectional views ofvarious operations in a process flow using a thin plate to supportlamination of ABF above a reference cavity, in accordance with anembodiment of the present invention.

Referring to FIG. 12A, a die 1202 (which may include an amplifier, etc.)is placed on a thin substrate 1204 (e.g., silicon, etc.) adjacent anelectrode 1206 (e.g., a copper electrode), above a metal holder 1200(e.g., a copper holder). A laminate organic dielectric film 1208 isdisposed above the structure of FIG. 12A, as depicted in FIG. 12B.Referring to FIG. 12C, via hole drilling and electroplating is performedto provide vias 1210 and copper layer 1212. A photoresist layer 1214 isthen formed and patterned to protect sensitive areas, as depicted inFIG. 12D. Referring to FIG. 12E, oxygen plasma release is then performedto remove a portion of organic dielectric film 1208 and to releasestructure 1216. Resist stripping is then performed to re-expose layer1212, as depicted in FIG. 12F. Referring to FIG. 12G, lamination of anorganic dielectric film 1218 is then performed. Via drilling andelectroplating is then performed to provide vias 1220 and copper layer1222, as depicted in FIG. 12H. Referring to FIG. 12I, organic dielectricfilm 1224 (e.g., ABF) is then laminated on the structure of FIG. 12H.Via drilling and electroplating is again performed to provide vias 1226and copper layer 1228, as depicted in FIG. 12J. Referring to FIG. 12K,photoresist layer 1230 is formed and patterned to protect sensitiveareas. An oxygen plasma release is the performed to release structure1232, as depicted in FIG. 12L. Referring to FIG. 12M, photoresist layer1230 is then stripped, re-exposing layer 1228. A pick and place approachis then performed to provide a thin plate 1234, as depicted in FIG. 12N.Referring to FIG. 12O, lamination of another insulator layer 1236 isthen performed above the structure of FIG. 12N. Via drilling andelectroplating is performed to provide vias 1238 and copper layer 1240,as depicted in FIG. 12P. Referring to FIG. 12Q, the copper holder 1200is then removed. A reference cavity 1250 and capacitor 1252 is thusformed.

Referring again to FIG. 12Q, the structure as depicted can be viewed asa completed package for the semiconductor die included therein. However,for specific implementations, an array of external contacts (e.g., BGAcontacts) may optionally be formed above or below the structure depictedin FIG. 12Q. The resulting structure may then be coupled to a printedcircuit board (PCB) or like receiving surface.

In a third example, FIGS. 13A-13T illustrate cross-sectional views ofvarious operations in a process flow for fabricating a magneticallyactuated pressure sensor, in accordance with an embodiment of thepresent invention.

Referring to FIG. 13A, a die 1302 (which may include an amplifier, etc.)is placed on a thin substrate 1304 (e.g., silicon, etc.) adjacent amagnet 1306, above a metal holder 1300 (e.g., a copper holder). Alaminate organic dielectric film 1308 is disposed above the structure ofFIG. 13A, as depicted in FIG. 13B. Referring to FIG. 13C, via holedrilling and electroplating is performed to provide vias 1310 and copperlayer 1312. A laminate organic dielectric film 1314 is then disposedabove the structure of FIG. 13C, as depicted in FIG. 13D. Referring toFIG. 13E, via hole drilling and electroplating is performed to providevias 1316 and copper layer 1318. A photoresist layer 1320 is then formedand patterned to protect sensitive areas, as depicted in FIG. 13F.Referring to FIG. 13G, oxygen plasma release is then performed to removea portion of organic dielectric film 1314 and to release structure 1322.Resist stripping is then performed to re-expose layer 1318, as depictedin FIG. 13H. Referring to FIG. 13I, a thin metal plate 1324 may beoptionally provided for support or, alternatively, a mesh structure maybe formed. Referring to FIG. 13J, lamination of an organic dielectricfilm 1326 is then performed. Via drilling and electroplating is thenperformed to provide vias 1328 and copper layer 1330, as depicted inFIG. 13K. Referring to FIG. 13L, organic dielectric film 1332 (e.g.,ABF) is then laminated on the structure of FIG. 13K. Via drilling andelectroplating is again performed to provide vias 1334 and copper layer1336, as depicted in FIG. 13M. Additionally (although not shown) a tracelayer including resonant beam coils may be formed during this processoperation. Referring to FIG. 13N, organic dielectric film 1338 is thenlaminated on the structure of FIG. 13M. Via drilling and electroplatingis again performed to provide vias 1340 and copper layer 1342, asdepicted in FIG. 13O. This operation may be used if, e.g., supportmeshing is to be formed. In such a case, plate protection mesh is formedas an optional structural support and is anchored at many locations notoccupied by MEMS structure. Referring to FIG. 13P, photoresist layer1344 is formed and patterned to protect sensitive areas. An oxygenplasma release is then performed to release structure 1346, as depictedin FIG. 13Q. Referring to FIG. 13R, photoresist layer 1344 is thenstripped, re-exposing layer 1342. Referring to FIG. 13S, lamination ofanother insulator layer 1348 is then performed above the structure ofFIG. 13R. The copper holder 1300 is then removed, as depicted in FIG.13T. A reference cavity 1350 and capacitor 1352 is thus formed, alongwith the embedded magnet 1306.

Referring again to FIG. 13T, the structure as depicted can be viewed asa completed package for the semiconductor die included therein. However,for specific implementations, an array of external contacts (e.g., BGAcontacts) may optionally be formed above or below the structure depictedin FIG. 13T. The resulting structure may then be coupled to a printedcircuit board (PCB) or like receiving surface.

With reference to FIGS. 11A-11P, 12A-12Q and 13A-13T, an air pressuresensor may be fabricated in BBUL layers. The BBUL layer may be part of alarger BBUL system. In general, BBUL is a processor packaging technologythat is bumpless since it does not use the usual small solder bumps toattach the silicon die to the processor package wires. It has build-uplayers since it is grown or built-up around the silicon die. Somesemiconductor packages now use a coreless substrate, which does notinclude the thick resin core layer commonly found in conventionalsubstrates. In an embodiment, as part of the BBUL process, electricallyconductive vias and routing layers are formed above the active side of asemiconductor die using a semi-additive process (SAP) to completeremaining layers.

An air pressure sensor may be formed in BBUL layers during packaging ofa semiconductor die on a panel of a carrier. The carrier may be providedhaving planar panels or panels with a plurality of cavities disposedtherein, each sized to receive a semiconductor die. During processing,identical structures may be mated in order to build a back-to-backapparatus for processing utility. Consequently, processing throughput iseffectively doubled. For example, a carrier may include panels with 1000recesses on either side, allowing for fabrication of 2000 individualpackages from a single carrier. The panel may include an adhesionrelease layer and an adhesive binder. A cutting zone may be provided ateach end of the apparatus for separation processing. A backside of asemiconductor die may be bonded to the panel with a die-bonding film.Encapsulating layers may be formed by a lamination process. In anotherembodiment, one or more encapsulation layers may be formed by spinningon and curing a dielectric upon a wafer-scale array of apparatuses.

Regarding the overall packaging process described in association withFIGS. 11A-11P, 12A-12Q and 13A-13T, in an embodiment, the substrateformed is a coreless substrate since a panel is used to support thepackaging of a semiconductor die through to formation of an array ofexternal conductive conducts. The panel is then removed to provide acoreless package for the semiconductor die. Accordingly, in anembodiment, the term “coreless” is used to mean that the support uponwhich the package was formed for housing a die is ultimately removed atthe end of a build-up process. In a specific embodiment, a corelesssubstrate is one that does not include a thick core after completion ofthe fabrication process. As an example, a thick core may be one composedof a reinforced material such as is used in a motherboard and mayinclude conductive vias therein. It is to be understood that die-bondingfilm may be retained or may be removed. In either case, inclusion orexclusion of a die-bonding film following removal of the panel providesa coreless substrate. Still further, the substrate may be considered acoreless substrate because it does not include a thick core such as afiber reinforced glass epoxy resin.

In an embodiment, an active surface of the packaged semiconductor dieincludes a plurality of semiconductor devices, such as but not limitedto transistors, capacitors and resistors interconnected together by adie interconnection structure into functional circuits to thereby forman integrated circuit. As will be understood to those skilled in theart, the device side of the semiconductor die includes an active portionwith integrated circuitry and interconnections. The semiconductor diemay be any appropriate integrated circuit device including but notlimited to a microprocessor (single or multi-core), a memory device, achipset, a graphics device, an application specific integrated circuitaccording to several different embodiments. In another embodiment, morethan one die is embedded in the same package. For example, in oneembodiment, a packaged semiconductor die further includes a secondarystacked die. The first die may have one or more through-silicon viasdisposed therein (TSV die). The second die may be electrically coupledto the TSV die through the one or more through-silicon vias. In oneembodiment, both dies are embedded in a coreless substrate.

The packaged semiconductor die may, in an embodiment, be a fullyembedded and surrounded semiconductor die. As used in this disclosure,“fully embedded and surrounded” means that all surfaces of thesemiconductor die are in contact with an encapsulating film (such as adielectric layer) of substrate, or at least in contact with a materialhoused within the encapsulating film. Said another way, “fully embeddedand surrounded” means that all exposed surfaces of the semiconductor dieare in contact with the encapsulating film of a substrate.

The packaged semiconductor die may, in an embodiment, be a fullyembedded semiconductor die. As used in this disclosure, “fully embedded”means that an active surface and the entire sidewalls of thesemiconductor die are in contact with an encapsulating film (such as adielectric layer) of a substrate, or at least in contact with a materialhoused within the encapsulating film. Said another way, “fully embedded”means that all exposed regions of an active surface and the exposedportions of the entire sidewalls of the semiconductor die are in contactwith the encapsulating film of a substrate. However, in such cases, thesemiconductor die is not “surrounded” since the backside of thesemiconductor die is not in contact with an encapsulating film of thesubstrate or with a material housed within the encapsulating film. In afirst embodiment, a back surface of the semiconductor die protrudes fromthe global planarity surface of the die side of a substrate. In a secondembodiment, no surface of the semiconductor die protrudes from theglobal planarity surface of the die side of a substrate.

In contrast to the above definitions of “fully embedded and surrounded”and “fully embedded,” a “partially embedded” die is a die having anentire surface, but only a portion of the sidewalls, in contact with anencapsulating film of a substrate (such as a coreless substrate), or atleast in contact with a material housed within the encapsulating film.In further contrast, a “non-embedded” die is a die having at most onesurface, and no portion of the sidewalls, in contact with anencapsulating film of a substrate (such as a coreless substrate), or incontact with a material housed within the encapsulating film.

As mentioned briefly above, an array of external conductive contacts maysubsequently be formed. In an embodiment, the external conductivecontacts couple the formed substrate to a foundation substrate. Theexternal conductive contacts may be used for electrical communicationwith the foundation substrate. In one embodiment, the array of externalconductive contacts is a ball grid array (BGA). In other embodiments,the array of external conductive contacts is an array such as, but notlimited to, a land grid array (LGA) or an array of pins (PGA).

In an embodiment, as described above, the substrate is a BBUL substrate.In one such embodiment, an air pressure sensor is embedded within thebuildup layers along with a semiconductor die. Although described indetail above for a BBUL process, other process flows may be usedinstead. For example, in another embodiment, a semiconductor die ishoused in a core of a substrate. In another embodiment, fan-out layersare used.

The term “MEMS” generally refers to an apparatus incorporating somemechanical structure having a dimensional scale that is comparable tomicroelectronic devices. The mechanical structure is typically capableof some form of mechanical motion and having dimensions belowapproximately 250 microns; however, some embodiments may include MEMSsensors that are a few millimeters across a package. Thus, MEMSstructures contemplated herein are, in an embodiment, any device thatfalls within the scope of MEMS technologies. For example, a MEMSstructure may be any mechanical and electronic structure having acritical dimension of less than approximately 250 microns and fabricatedusing lithography, deposition, and etching processes above a substrate.In accordance with an embodiment of the present invention, the MEMSstructure is a device such as, but not limited to, a resonator, asensor, a detector, a filter or a mirror. In one embodiment, the MEMSstructure is a resonator. In a specific embodiment, the resonator is onesuch as, but not limited to, a beam, a plate and a tuning fork or acantilever arm. In an embodiment, an electroplated copper layer is usedto form a hermetic seal for a reference air pressure cavity for a MEMSbased air pressure sensor.

Embodiments of the present invention may be suitable for fabricating asystem on a chip (SOC), e.g., for a smartphone or a tablet. In anembodiment, an air pressure sensor is integrated and fabricated in aBBUL packaging fab. The same backend processing used for existing BBULcoreless packaging may be used as a base flow. Alternatively, theprocess flow for die integration with MEMS may be applicable to otherpackaging substrate technologies.

FIG. 14 is a schematic of a computer system 1400, in accordance with anembodiment of the present invention. The computer system 1400 (alsoreferred to as the electronic system 1400) as depicted can embody asemiconductor package having an air pressure sensor according to any ofthe several disclosed embodiments and their equivalents as set forth inthis disclosure. The computer system 1400 may be a mobile device such asa netbook computer. The computer system 1400 may be a mobile device suchas a wireless smart phone. The computer system 1400 may be a desktopcomputer. The computer system 1400 may be a hand-held reader. Thecomputer system 1400 may be a watch.

In an embodiment, the electronic system 1400 is a computer system thatincludes a system bus 1420 to electrically couple the various componentsof the electronic system 1400. The system bus 1420 is a single bus orany combination of busses according to various embodiments. Theelectronic system 1400 includes a voltage source 1430 that providespower to the integrated circuit 1410. In some embodiments, the voltagesource 1430 supplies current to the integrated circuit 1410 through thesystem bus 1420.

The integrated circuit 1410 is electrically coupled to the system bus1420 and includes any circuit, or combination of circuits according toan embodiment. In an embodiment, the integrated circuit 1410 includes aprocessor 1412 that can be of any type. As used herein, the processor1412 may mean any type of circuit such as, but not limited to, amicroprocessor, a microcontroller, a graphics processor, a digitalsignal processor, or another processor. In an embodiment, the processor1412 includes or is included in a semiconductor package having an airpressure sensor, as disclosed herein. In an embodiment, SRAM embodimentsare found in memory caches of the processor. Other types of circuitsthat can be included in the integrated circuit 1410 are a custom circuitor an application-specific integrated circuit (ASIC), such as acommunications circuit 1414 for use in wireless devices such as cellulartelephones, smart phones, pagers, portable computers, two-way radios,and similar electronic systems. In an embodiment, the processor 1410includes on-die memory 1416 such as static random-access memory (SRAM).In an embodiment, the processor 1410 includes embedded on-die memory1416 such as embedded dynamic random-access memory (eDRAM).

In an embodiment, the integrated circuit 1410 is complemented with asubsequent integrated circuit 1411. Useful embodiments include a dualprocessor 1413 and a dual communications circuit 1415 and dual on-diememory 1417 such as SRAM. In an embodiment, the dual integrated circuit1410 includes embedded on-die memory 1417 such as eDRAM.

In an embodiment, the electronic system 1400 also includes an externalmemory 1440 that in turn may include one or more memory elementssuitable to the particular application, such as a main memory 1442 inthe form of RAM, one or more hard drives 1444, and/or one or more drivesthat handle removable media 1446, such as diskettes, compact disks(CDs), digital variable disks (DVDs), flash memory drives, and otherremovable media known in the art. The external memory 1440 may also beembedded memory 1448 such as the first die in an embedded TSV die stack,according to an embodiment.

In an embodiment, the electronic system 1400 also includes a displaydevice 1450 and an audio output 1460. In an embodiment, the electronicsystem 1400 includes an input device such as a controller 1470 that maybe a keyboard, mouse, trackball, game controller, microphone,voice-recognition device, or any other input device that inputsinformation into the electronic system 1400. In an embodiment, an inputdevice 1470 is a camera. In an embodiment, an input device 1470 is adigital sound recorder. In an embodiment, an input device 1470 is acamera and a digital sound recorder.

As shown herein, the integrated circuit 1410 may be implemented in anumber of different embodiments, including a semiconductor packagehaving an air pressure sensor according to any of the several disclosedembodiments and their equivalents, an electronic system, a computersystem, one or more methods of fabricating an integrated circuit, andone or more methods of fabricating an electronic assembly that includesa semiconductor package having an air pressure sensor according to anyof the several disclosed embodiments as set forth herein in the variousembodiments and their art-recognized equivalents. The elements,materials, geometries, dimensions, and sequence of operations can all bevaried to suit particular I/O coupling requirements including arraycontact count, array contact configuration for a microelectronic dieembedded in a processor mounting substrate according to any of theseveral disclosed semiconductor package having an air pressure sensorembodiments and their equivalents. A foundation substrate may beincluded, as represented by the dashed line of FIG. 14. Passive devicesmay also be included, as is also depicted in FIG. 14.

Embodiments of the present invention include semiconductor packages withair pressure sensors.

In an embodiment, a semiconductor package includes a plurality ofbuild-up layers. A cavity is disposed in one or more of the build-uplayers. An air pressure sensor is disposed in the plurality of build-uplayers and includes the cavity and an electrode disposed above thecavity.

In one embodiment, the cavity is a hermetically sealed cavity.

In one embodiment, the hermetically sealed cavity is composed of acontinuous via ring.

In one embodiment, one or more of the build-up layers having thehermetically sealed cavity disposed therein is an Anjinomoto build-upfilm (ABF) layer, and the continuous via ring is composed of copper.

In one embodiment, the air pressure sensor includes a MEMS device.

In one embodiment, a diaphragm of the MEMS device includes the cavity,and the electrode includes a suspended portion of the MEMS device.

In one embodiment, the suspended portion of the MEMS device is composedof copper.

In one embodiment, the semiconductor package further includes a layerhaving a mesh pattern disposed in the cavity, the layer providingstructural support for the cavity.

In one embodiment, the semiconductor package further includes a thinmetal plate disposed between the cavity and the electrode, the thinmetal plate providing structural support for the cavity.

In one embodiment, the cavity provides a reference pressure for the airpressure sensor.

In one embodiment, wherein the semiconductor package further includes abumpless build-up layer (BBUL) substrate.

In one embodiment, the BBUL substrate is a coreless substrate.

In an embodiment, a semiconductor package, includes a substrate composedof a plurality of build-up layers. A semiconductor die is housed in thesubstrate. A cavity is disposed in one or more of the build-up layers,above the semiconductor die. An air pressure sensor is disposed in theplurality of build-up layers and includes the cavity and an electrodedisposed above the cavity. The electrode is electrically coupled to thesemiconductor die. The semiconductor package also includes one or moreopenings exposing a portion of the air pressure sensor to air pressureambient to the semiconductor package.

In one embodiment, the substrate is a bumpless build-up layer (BBUL)substrate.

In one embodiment, the BBUL substrate is a coreless substrate.

In one embodiment, the cavity is a hermetically sealed cavity.

In one embodiment, the hermetically sealed cavity is composed of acontinuous via ring.

In one embodiment, one or more of the build-up layers having thehermetically sealed cavity disposed therein is an Anjinomoto build-upfilm (ABF) layer, and the continuous via ring is composed of copper.

In one embodiment, the air pressure sensor includes a MEMS device.

In one embodiment, a diaphragm of the MEMS device includes the cavity,and the electrode includes a suspended portion of the MEMS device.

In one embodiment, the suspended portion of the MEMS device is composedof copper.

In one embodiment, the MEMS device is disposed proximate to an activesurface of the semiconductor die and distal from a back surface of thesemiconductor die.

In one embodiment, the semiconductor package further includes a layerhaving a mesh pattern disposed in the cavity, the layer providingstructural support for the cavity.

In one embodiment, the semiconductor package further includes a thinmetal plate disposed between the cavity and the electrode, the thinmetal plate providing structural support for the cavity.

In one embodiment, the cavity provides a reference pressure for the airpressure sensor.

In one embodiment, the semiconductor package further includes apermanent magnet coupled with the air pressure sensor.

In an embodiment, a method of sensing air pressure ambient to asemiconductor package includes determining an extent of capacitivecoupling between a diaphragm of an air pressure sensor and an electrodeof the air pressure sensor. The diaphragm includes a hermetically sealedcavity disposed below the electrode and in build-up layers of thesemiconductor package. The hermetically sealed cavity has a referencepressure. The method also includes correlating the extent of capacitivecoupling with a difference between the reference pressure and theambient pressure.

In one embodiment, the diaphragm reduces the size of the hermeticallysealed cavity, and increases a distance between the diaphragm and theelectrode, when the ambient air pressure is greater than the referencepressure.

In one embodiment, the diaphragm increases the size of the hermeticallysealed cavity, and decreases a distance between the diaphragm and theelectrode, when the ambient air pressure is less than the referencepressure.

In one embodiment, the air pressure sensor includes a resonant beam. Themethod further includes actuating the resonant beam through interactionof an AC current with a permanent magnet. A diaphragm deflection is dueto a difference in air pressure and transduces a Z-displacement whichapplies tension onto the resonant beam and increases a resonantfrequency of the resonant beam.

What is claimed is:
 1. A semiconductor package, comprising: a pluralityof build-up layers; a cavity disposed in one or more of the build-uplayers; and an air pressure sensor disposed in the plurality of build-uplayers and comprising the cavity and an electrode disposed above thecavity.
 2. The semiconductor package of claim 1, wherein the cavity is ahermetically sealed cavity.
 3. The semiconductor package of claim 2,wherein the hermetically sealed cavity comprises a continuous via ring.4. The semiconductor package of claim 3, wherein one or more of thebuild-up layers having the hermetically sealed cavity disposed thereinis an Anjinomoto build-up film (ABF) layer, and wherein the continuousvia ring comprises copper.
 5. The semiconductor package of claim 1,wherein the air pressure sensor comprises a MEMS device.
 6. Thesemiconductor package of claim 5, wherein a diaphragm of the MEMS devicecomprises the cavity, and wherein the electrode comprises a suspendedportion of the MEMS device.
 7. The semiconductor package of claim 6,wherein the suspended portion of the MEMS device comprises copper. 8.The semiconductor package of claim 1, further comprising: a layer havinga mesh pattern disposed in the cavity, the layer providing structuralsupport for the cavity.
 9. The semiconductor package of claim 1, furthercomprising: a thin metal plate disposed between the cavity and theelectrode, the thin metal plate providing structural support for thecavity.
 10. The semiconductor package of claim 1, wherein the cavityprovides a reference pressure for the air pressure sensor.
 11. Thesemiconductor package of claim 1, further comprising: a bumplessbuild-up layer (BBUL) substrate.
 12. The semiconductor package of claim11, wherein the BBUL substrate is a coreless substrate.
 13. Asemiconductor package, comprising: a substrate comprising a plurality ofbuild-up layers; a semiconductor die housed in the substrate; a cavitydisposed in one or more of the build-up layers, above the semiconductordie; an air pressure sensor disposed in the plurality of build-up layersand comprising the cavity and an electrode disposed above the cavity,the electrode electrically coupled to the semiconductor die; and one ormore openings exposing a portion of the air pressure sensor to airpressure ambient to the semiconductor package.
 14. The semiconductorpackage of claim 13, wherein the substrate is a bumpless build-up layer(BBUL) substrate.
 15. The semiconductor package of claim 14, wherein theBBUL substrate is a coreless substrate.
 16. The semiconductor package ofclaim 13, wherein the cavity is a hermetically sealed cavity.
 17. Thesemiconductor package of claim 16, wherein the hermetically sealedcavity comprises a continuous via ring.
 18. The semiconductor package ofclaim 17, wherein one or more of the build-up layers having thehermetically sealed cavity disposed therein is an Anjinomoto build-upfilm (ABF) layer, and wherein the continuous via ring comprises copper.19. The semiconductor package of claim 13, wherein the air pressuresensor comprises a MEMS device.
 20. The semiconductor package of claim19, wherein a diaphragm of the MEMS device comprises the cavity, andwherein the electrode comprises a suspended portion of the MEMS device.21. The semiconductor package of claim 20, wherein the suspended portionof the MEMS device comprises copper.
 22. The semiconductor package ofclaim 19, wherein the MEMS device is disposed proximate to an activesurface of the semiconductor die and distal from a back surface of thesemiconductor die.
 23. The semiconductor package of claim 13, furthercomprising: a layer having a mesh pattern disposed in the cavity, thelayer providing structural support for the cavity.
 24. The semiconductorpackage of claim 13, further comprising: a thin metal plate disposedbetween the cavity and the electrode, the thin metal plate providingstructural support for the cavity.
 25. The semiconductor package ofclaim 13, wherein the cavity provides a reference pressure for the airpressure sensor.
 26. The semiconductor package of claim 13, furthercomprising: a permanent magnet coupled with the air pressure sensor. 27.A method of sensing air pressure ambient to a semiconductor package, themethod comprising: determining an extent of capacitive coupling betweena diaphragm of an air pressure sensor and an electrode of the airpressure sensor, the diaphragm comprising a hermetically sealed cavitydisposed below the electrode and in build-up layers of the semiconductorpackage, the hermetically sealed cavity having a reference pressure; andcorrelating the extent of capacitive coupling with a difference betweenthe reference pressure and the ambient pressure.
 28. The method of claim27, wherein the diaphragm reduces the size of the hermetically sealedcavity, and increases a distance between the diaphragm and theelectrode, when the ambient air pressure is greater than the referencepressure.
 29. The method of claim 27, wherein the diaphragm increasesthe size of the hermetically sealed cavity, and decreases a distancebetween the diaphragm and the electrode, when the ambient air pressureis less than the reference pressure.
 30. The method of claim 27, whereinthe air pressure sensor comprises a resonant beam, the method furthercomprising actuating the resonant beam through interaction of an ACcurrent with a permanent magnet, wherein a diaphragm deflection is dueto a difference in air pressure and transduces a Z-displacement whichapplies tension onto the resonant beam and increases a resonantfrequency of the resonant beam.